Demand for integrated circuits (ICs) in portable electronic applications has motivated greater levels of semiconductor device integration. Many advanced semiconductor devices in development leverage non-silicon semiconductor materials, a subset of which have wurtzite crystallinity. Exemplary wurtzite materials include AgI, ZnO, CdS, CdSe, α-SiC, BN, GaN, AlN, the last two of which may be grouped together as being in the III-N material system. The III-N material system shows particular promise for high voltage and high frequency applications like power management ICs (PMICs) and RF power amplifiers (PAs). III-N heterostructure field effect transistors (HFETs), such as high electron mobility transistors (HEMT) and metal oxide semiconductor (MOS) HEMT, employ a semiconductor heterostructure with one or more heterojunction. One heterojunction is often at an interface of a GaN semiconductor crystal and another III-N semiconductor alloy, such as AlGaN or AlInN. GaN-based HFET devices benefit from a relatively wide bandgap (˜3.4 eV), enabling higher breakdown voltages than Si-based MOSFETs, as well as high carrier mobility. The III-N material system is also useful for photonics (e.g., LEDs), photovoltaics, and sensors, one or more of which may be useful to integrate into an electronic device platform.
Multi-chip integration approaches have been employed to integrate silicon-based devices with those based on wurtzite semiconductor materials. These multi-chip approaches have scaling and performance limitations. Monolithic integration of silicon-based devices (e.g., CMOS field effect transistors) with devices utilizing the wurtzite material system is a challenge due to a large lattice mismatch (e.g., ˜41% between GaN and Si) and a large thermal expansion coefficient mismatch (e.g., ˜116% between Si and GaN). However, from a commercial standpoint, it is advantageous to integrate III-N transistors into the silicon fabrication infrastructure to take advantage of the economies of scale brought by 300 mm/450 mm wafer processing.